This invention generally relates to rotational velocity sensors, and more particularly to pulse signals corresponding to rotational velocity, for example pulse signals generated via a wheel speed sensor for a motor vehicle.
Applicants are unaware of any logistic systems that actually detect a broken tooth in a pulse signal. Instead, traditionally, a rapid wheel speed change due to a broken tooth in a pulse signal or missing/deviation of a wheel sensor has been determined by utilizing changes in a wheel speed acceleration. For example, there exists a method of detecting a failure of a wheel speed sensor typically due to a broken tooth by utilizing unusual rapid changes in a wheel speed when a phenomenon satisfies a predetermined condition.
The aforementioned traditional method reserves a certain degree of tolerance in a threshold value of ascertaining the failure in the wheel speed sensor in order to avoid a false detection. For that reason, there exists a difficulty in detecting a minor failure, and a few broken teeth of the wheel speed sensor might not have triggered the detection of such failure. Further, the traditional method typically cannot detect broken teeth the result from an eccentricity and/or iron powder adhesion typical but unique for an active sensor.
It is an object of this invention to provide a method or device facilitating a detection of a broken tooth in a pulse signal.
In a first aspect, a method of detecting a broken tooth in a pulse signal includes measuring one pulse cycle and another pulse cycle in almost constant speed, and determining whether a ratio of the one pulse cycle and the another pulse cycle is a multiplied number.
In a second aspect a method of detecting a broken tooth in a pulse signal as above, further includes measuring the one pulse cycle and N times of pulse cycle in case that the number of sensoring teeth is N, and a step of comparing measured values of the one pulse cycle and N times of pulse cycle.
In a third aspect a method of detecting a broken tooth in a pulse signal as above, further includes counting the number of the instances when the ratio of one pulse cycle and the another pulse cycle is a multiplied number, and a step of detecting a broken tooth if a counted value is a predetermined counting value or more
In a fourth aspect a method of detecting a broken tooth in a pulse signal as above, further includes counting the number of the instances when the ratio of one pulse cycle and the another pulse cycle is almost an odd-multiplied number at every counter, and a step of detecting a broken tooth if a counted value is a predetermined counting value or more.
In yet a further aspect a device for detecting a broken tooth in a pulse signal comprising a pulse cycle measuring means to measure one pulse cycle and another pulse cycle in almost constant speed, a comparing means to determine whether a ratio of one pulse cycle and another pulse cycle is a multiplied number, a counter counting the number of the instances when ratio of said one pulse cycle and another pulse cycle is a multiplied number, and a judging means to detect a broken tooth if a counted value is a predetermined counting value or more.